Continuous disc type press



April 23, 1963 A. J. A. ASPLUND CONTINUOUS DISC TYPE PRESS 2Sheets-Sheet 1 Filed Oct. 24, 1958 April 23, 1963 A. J. A. ASPLUNIDCONTINUOUS DISC TYPE PRESS 2 Sheets-Sheet 2 Filed Oct. 24, 1958 UnitedStatesPatent ()fifice 3,086,453 CONTINUOUS DISC TYPE PRESS Arne JohanArthur Asplund, 11 Orevagen, Bromma, Sweden Filed Oct. 24, 1958, Ser.No. 769,366 Claims priority, application Sweden Oct. 28, 1957 9 Claims.(Cl. 100-106) This invention relates to a continuous disc type press forexpelling liquid from wet material such as liquid 3,086,453 PatentedApr. 23, 1963 to this reduction of the fibre losses the cross section ofthe perforations in the discs may be made larger than suspensions ofcellulose fibres, bark particle-s, peat and the like, and of the kindcomprising two spaced perforated pressing discs disposed substantiallyco-axially on shafts having their axes disposed at a slight mutualinclination and rotating in the same direction, at least one of thediscs being axially movable and being subjected to forces tending topress the discs together and wherein the material to be treated is fedbetween the discs at a zone where the disc interspace is relativelylarge and the compression of the material is effected while beingcarried along by the rotation of the disc to the narrowest zone of saidinterspace.

Usually the shafts of the discs are approximately horizontal and thewidest zone of the interspace, the socalled gap, will then be positionedabove the shafts whereas the narrowest zone of the interspace, or thesocalled nip, is disposed below said shafts.

In presses of this kind hitherto constructed the suspension of materialand liquid is fed to the press by means of a screw conveyer or a similardevice. If the suspension is relatively dilute it must be thickened infront of the screw conveyer. This thickening operation is necessitatedby the fact that thin suspensions manage to pass through the spacebetween the perforated discs before a layer of the material, such asfibres, bark particles and the like, effective as a filter layer hasbeen built up, and that the suspension will not be sufficientlythickened to be caught by. the nip.

One object of the invention is to provide a press adapted to produceeffective compression in the press of suspensions sufiiciently dilutedas to be capable of being pumped to the press so that conduits may beused for conveying the suspension to the inlet of the press instead of ascrew conveyor which implies considerable reduction in the costs ofconstruction, operation and maintenance.

According to one main feature of the present invention the discs areconstructed to provide behind the perforations peripherally spaced cellspreferably of sector-shape communicating with the disc interspacethrough the perforations and, also with a device, such as a valvemember, acting to connect the cells to a source of vacuum or to anoutlet during part of each revolution of the discs.

By this construction a vacuum may thus be created in the cellsindependently of the expression of liquid effected while the material ispassing from the gap to the nip, whereas the finally treated material isdischarged from a zone of the interspace which communicates freely withthe surrounding atmosphere so that the cells through the perforationsare then open to atmospheric pressure. The vacuum vigorously promotesthe thickening of the suspension since the separation of the liquid isproduced more quickly.

According to another main feature of the invention a vacuum may be usedfor sucking out two liquid fractions separately from one another. Thefirst fraction consists of liquid which is separated through that cellor those cells which first receive the suspension entering the pressduring the rotation of the press discs. This first fraction separatedhas a comparatively large content of dry substance, such as fibres,which may be recovered, for instance, by the fraction being re-cycled tothe press. Due

hitherto. In practice this feature implies that the press can operatewith a high capacity, calculated on the discharged dewatered substance.The second fraction separated is relatively free from fibres and may besubjected to an evaporation process for recovery of chemicals dissolvedor suspended in the liquid, which is usually water.

Further objects and advantages of the invention will become apparentfrom the following description, considered in connection with theaccompanying drawings, which form part of this specification and inwhich:

FIG. 1 shows a side elevation partly in section of a press constructedaccording to the invention, the section being taken along the line I-Iof FIG. 2, FIG. 2 is a transverse section along the line IIII of FIG. 1.

Referring to the drawings numeral 10 designates a supporting frame of apress including two press discs 12, 14 rotatably mounted on said frame.Each disc has a hub portion 16 rigidly secured to a flange 18 of a shaft20 by means of a ring member 27 and bolts 24. Within the frame 10 and abearing housing 26, which is attached to the frame by means of bolts 25,is arranged a sleeve 28 contacting the bearing housing along twopreferably cylindrical surfaces, 30, 32 and axially slidable in relationto said housing. The sleeve 28 is held against rotation by means of abolt 34 entering an axially elongated aperture 36 in said sleeve. Theshaft 20 is rotatably mounted in the sleeve 28 by means of two bearings'38, 40. The two bearings and the sleeve 28 are thus axially fixedrelatively to the shaft 20.

The discs 12 and 14 have their shafts mounted substantially coaxially atadjacent ends, the shafts being slightly inclined to one another in thevertical plane and preferably also in the horizontal plane. In theembodiment shown the opposing faces of the discs are disposed so as toform an inwardly tapering interspace. Due to the slight inclination ofthe two shafts 20 the discs form an interspace which is wider above thanbelow the shafts. The maximum interspace will hereinafter be referred toas the gap and the minimum interspace as the nip. When the press discsrotate counter-clockwise as viewed in FIG. 2, the gap and the nip may bepositioned along a line 41 which is angularly displaced relatively to avertical longitudinal plane through the press. The discs 12, 14 arerotated in the same direction and with the same slow speed by means of atransmission, one for each disc. A transmission gear wheel 42 secured toeach disc is shown in the figures.

The discs are provided with peripheral walls 44 which, together with thehub portion 16 bound a cavity divided into a plurality of peripherallyspaced sector-shaped cells 46 by means of radially extending partitions45 or the like. Each cell 46 thus has circumferential and side wallssealing the cell with respect to the atmosphere and is covered by ascreen plate 48 on the active face of the disc. One screen plate may beprovided for each cell or may cover several cells. The cells areseparated from one another or said face by radial ribs 50 locatedopposite the partition 45. The outer surfaces of the ribs 50 and theplates 48 are flush or approximately flush with one another. The plates48 are perforated as indicated at 52 in FIG. 2, and the discs are formedwith bores 54 providing communication of the various cells with the rearface of the plates. The disc face contacted by the plates may beprovided with small transverse channels so as to establish communicationbetween the perforations 52 of the plates and the bores 54 which latterare substantially less in number. The discs are stiffened by webs 56between which are located the bores 54.

The interspace between the discs is covered externally by an annularcasing 58 and internally by a sleeve 60 both members having a greateraxial width at the upper edge than at the lower edge of the discscorresponding to the varying width of the interspace. The suspension tobe treated is introduced through an inlet 62 disposed adjacent the gap,and the treated material is discharged through an outlet 64 disposedbeyond the nip reckoned in the direction of rotation of the discsindicated by the arrow 66 in FIG. 2. Between the inlet 62 and the outlet64 a section of the interspace is occupied by a doctor 68 preferably insealing contact with the discs by means of pressure pads 70 made ofresilient material, such as rubber, and disposed in recesses in thedoctor.

Within each of the cells 46 pipes 72 extend from the hub portion 16outwards to the periphery of the cells and preferably terminate at thetrailing side of the cell which is lowermost during the downwardsdiverted part of the rotation of the discs. From the respective pipes 72channels 74 extending radially inwardly are formed in the flange 18 ofthe shaft and in a bush 76 secured to the flange. In the bush isarranged a valve member having the form of a stationary slide member 78.From the slide member 78 a tube 80 attached to the member 78 extendsthrough the hollow interior of the shaft to a conduit 82 disposedexternally of the shaft and communicating with a vacuum pump 84. Theslide member 78 is provided with a plurality of radial channels 86connecting the interior of the tube 80 with the pipes 72 located in thelower section of the press during the rotation of the discs.Consequently the pipes 72 in the cells designated 46a-d in FIG. 2communicate with the vacuum pump 84 through the tube 80 while theremaining cells are disconnected from the pump 84.

Another group of radial passages 88 from the individual cells 46 extendthrough the hub 16, the flange 18 and the bush 76 into the slide member78. These passages thus open at the inner periphery of the cells. Theslide member 78 has a number of radial channels 90 mating with thepassages 88, and opening into an annular chamber 92 bounded by the tube80 and a tube 94 disposed co-axially with and surrounding the tube 80.The annular chamber communicates with a conduit 96 connected to a secondvacuum pump 98. The pumps 84 and 98 may be used to create a negativepressure in the cells of the order of 4 or meters of water column.

The conduits 82 and 96 are connected to a sleeve 100 projecting into theend portion of the shaft 20 and held stationary by means of an arm 102engaging a pin 104 secured to the stationary frame. The tubes 80 and 94have their outer ends tightly connected to the sleeve 100. Thus theslide member 78 is thereby intimately connected to the sleeve 100 andmay be withdrawn from the shaft 20 by means of said sleeve. The slidemember 78 may be adjusted to various angular positions in order tochange the position of the passage openings.

The channels 90 in the slide member are so disposed as to providecommunication between the annular chamber 92 and only those cells whichfirst receive the incoming liquid suspension. These cells may, forexample, be those designated 46e-g in FIG. 2. The other cells are cutoff from the channels 90.

One or more of the passages 88 communicating with the cells in positions46a-d during rotation of the discs 12, 14 may be in communication withthe outer atmosphere through small passage ways 106 provided in theslide member 78, the annular chamber 108 between the tube 94 and theshaft 20, and a channel 110 in the sleeve 100 in order to supply air tosaid cells. A narrow tube 112 for pressure liquid such as water leads toone or more radial passages 114 in the slide member 78 opening into thesealing surf-aces between the slide member and the bush 76. The supplyof water under pressure to the sealing surfaces and grooves formed inthese surfaces in known manner counteracts undesired leakage between thevarious systems of passages in the multi-way valve formed by the slidemember 78 and the bush 76.

The counter-pressure acting axially on the discs 12, 14 and opposing thepressure exerted by the material under compression may with advantage beestabilshed by means of hydraulic servo-systems 116 positioned below theshafts 20. The fluid pressure in the various servo-systems istransferred through the intermediary of a plunger 118 to one end of alever 120 mounted on a pivot pin 122 carried in a fixed bracket 124.Between the ends of the lever 120 a backing roller 126 is rotatablymounted, said backing roller having a curved or part-spherical rollerface 128 adapted to co-operate with a roller track 130 of correspondingtransverse contour formed in a ring member 132, secured together withthe gear wheel 42 to the wall 44 of the disc by means of bolts 134.Preferably three servo-systems are mounted to cooperate with each disc12 and 14, respectively. By means of the lever 120 the pressure exertedon the ring 132 by the backing roller 126 will be twice as large as thepressure acting in the servo-system. This device is described more indetail in the specification of my copending patent application No.769,367 of even date herewith and to which reference may be made for afuller description.

A labyrinth seal 136 is provided between the external casing 58 and thediscs 12 and 14. Liquid leaking out through said seal is collected in agutter 138 which has a drain 140 at the bottom.

The thin suspension of, for instance, water (liquor) and cellulosefibres is preferably pumped in through the inlet 62 and enters theinterspace between the discs at the top section of the interspace asshown in FIG. 2. The cells 46e-g adjacent the inlet communicate with thepump 98 and a strong removal of water by suction is effected through thecells exposed to the vacuum. Durmg this step of the treatment a fibrelayer settles on the screen plates 48, but as this layer is stillcomparatively thru a rather large quantity of the fibres follows thewater sucked out. These fibres are recovered, for example by re-cyclingthe fraction passing the pump 98 to the press where it is mixed withsuspension not yet treated.

When the cells pass over from, for example, the position 46g to 46a theconnection with the pump 98 is interrupted and a communication isestablished between the cells and the pump 84. The fraction nowexpressed from the pulp suspension is substantially free from fibres dueto the fact that the fibre layer on the disc screens 48 has been builtup to a greater thickness. At the same time an is ntroduced into thecells through the passage way 106 with throttling, so that the incomingair quantity is substantially equal to the water quantity sucked away inunit time. In this manner the water may be discharged without any riskof destroying the vacuum prevailing in the cells. The expression ofwater is continued until the material has passed the narrowest section,that is the nip, located at the lower part of the line 41. The discsafter having passed this line, again diverge, and when the materialstrikes the doctor 68 it is scraped off from the discs and dischargedthrough the outlet 64. When the cells are in this section of arevolution they communicate with the outer atmosphere and are also cutoff from both vgcuum pumps by means of the valve member described a ove.

In some cases a single vacuum system may be sufiicient. In this case thecells may be provided with pockets at their trailing portions, eachpocket starting from the rear wall of the cell, at the portion of thecell located radially nwardly and extending radially outwardly butterminatlng slightly spaced from the peripheral external wall of thecell. While the cell rotates upwardly as viewed in FIG. 2, liquid willcollect and be retained in the pocket. The liquid may then be conductedaway through a channel passing inwardly at the hub portion of the discand 23 through a valve element to a drain, when the cell is positionedat another part of the revolution, for example above the shaft. Thesources of vacuum may be replaced by devices permitting the liquid inthe cells to flow ofi by gravity, for example by removal of screws plugs135 allowing the pump 84 to be dispensed with. In a similar mannerescape due to gravity may be arranged through the passages 88 so as torender the pump 98 superfluous.

While one more or less specific embodiment 'of the invention has beenshown and described it is to be understood that this is for purpose ofillustration only and that the invention is not to be limited thereby,but its scope is to be determined by the appended claims.

What I claim is:

1. A disc type press for expressing liquid from a liquid suspension ofcellulose fibres, bark particles, peat or the like, comprising twofacially opposed discs provided with perforations and arrangedsubstantially coaxially, which discs are urged toward one another, eachof the discs having a slight inclination of its axis to thereby providea relatively large space between the upper portions of the discs and asmaller space between the lower portions,

said discs being rotated in the same direction, the material to becompressed being introduced through an inlet between the discs where thespace between the latter is comparatively large, the expressing ofliquid from the material taking place while the material is carried bythe rotation of the discs, :along the narrowest portion of the spacebetween the discs and thereafter discharged, the discs being eachprovided with a plurality of separate peripherally spaced cells behindthe perforations, said cells being formed by intermediate wallsextending radially and axially from the discs on the sides thereofremote from the space between the discs, said cells being closed bywalls extending substantially parallel to the discs on opposite sides ofsaid intermediate walls, said cells in each disc being separated fromone another and being of sector shape, the cells having one side incommunication with the perforations and the other side provided withindividual pass-ages so located that draining the liquid from one celltakes place during only a portion of one rotation of the discs, asuction source for aiding in said draining, each of said cells beingprovided with two outlet passages arranged to drain the liquid from theperforations in the discs during different portions of the rotationalcycle whereby the liquid will form two different fractions.

2. A press according to claim 1 characterized by the fact that the twooutlet passages from a single cell are each connected to its own channelwhich extends through an axle in the discs.

3. A press according to claim 1 characterized by the fact that the twooutlet passages belonging to one cell are each connected to its ownrespective vacuum source.

4. A press according to claim 3 characterized by the fact that one ofthe outlet passages belonging to one cell joins said cell at the innerperiphery of the same while the other outlet passage for said cell joinsthe same at its outer periphery.

5. A press according to claim 4 characterized by the fact that thefirst-mentioned outlet passage is arranged to connect with thecorresponding channel in the axle only when the cell, during itsrotation is located above the axle and the other outlet passage connectswith its channel only when the cell is located below the axle.

6. A press according to claim 5 characterized by the fact that astationary slide is arranged in the axle, said slide abutting tightlyagainst the axle, the portion of the axle against which the slide abutsbeing provided with channels corresponding to the respective outletpassages of the cells in order to establish connection with theaxially-extending channels at predetermined times.

7. A press according to claim 6 characterized by the fact that the slideis arranged to admit air under throttling to one or more of the cellsthrough a channel when outlet passages joining the outer periphery areconnected with a vacuum source.

8. A press according to claim 6 characterized by the fact that on theopposing sides of the discs there are plates having perforations thesize of which corresponds to that of the cells and by means of whichcommunication is established with the cells through channels in thediscs.

9. A disc type press for expressing liquid from liquid suspension ofcellulose fibres, bark particles, peat or the like, comprising, twofacially opposed discs provided with perforations and arrangedsusbtantially co-axially, which discs are urged toward one another, eachof the discs having a slight inclination of its axis to thereby providea relatively large space between the upper portions of the discs and asmaller space between the lower portions, said discs being rotated inthe same direction, the material to be compressed being introducedthrough an inlet between the discs where the space between the latter iscomparatively large, the expressing of liquid from the material takingplace while the material is carried by the rotation of the discs alongto the narrowest portion of the space between the discs and thereafterdischarged, the discs being each provided with a plurality of separate,peripherally spaced cells behind the perforations, said cells beingformed by intermediate walls extending radially and axially from thediscs on the sides thereof remote from the space between the discs, saidcells being closed by walls extending substantially parallel to thediscs on opposite sides of said intermediate walls, said cells in eachdisc being separated from one another and being of sector shape, thecells having one side in communication with the perforations and theother side provided with individual outlet passages so located thatdraining the liquid from one cell takes place during only a portion ofone rotation of the discs, a hollow axle provided in each of the discsto provide a channel, the outlet passages from the individual cellsbeing in communication with the channel only during a portion of onerotation of the discs.

References Cited in the file of this patent UNITED STATES PATENTS241,243 Selwig May 10, 1881 670,963 Logemann Apr. 2, 1901 2,084,229 VanMaaven June 15, 1937 2,226,926 Gordon Dec. 31, 1940 2,617,354 IngallsNov. .11, 1952

1. A DISC TYPE PRESS FOR EXPRESSING LIQUID FROM A LIQUID SUSPENSION OFCELLULOSE FIBRES, BARK PARTICLES, PEAT OR THE LIKE, COMPRISING TWOFACIALLY OPPOSED DISCS PROVIDED WITH PERFORATIONS AND ARRANGEDSUBSTANTIALLY COAXIALLY, WHICH DISCS ARE URGED TOWARD ONE ANOTHER, EACHOF THE DISCS HAVING A SLIGHT INCLINATION OF ITS AXIS TO THEREBY PROVIDEA RELATIVELY LARGE SPACE BETWEEN THE UPPER PORTIONS OF THE DISCS AND ASMALLER SPACE BETWEEN THE LOWER PORTIONS, SAID DISCS BEING ROTATED INTHE SAME DIRECTION, THE MATERIAL TO BE COMPRESSED BEING INTRODUCEDTHROUGH AN INLET BETWEEN THE DISCS WHERE THE SPACE BETWEEN THE LATTER ISCOMPARATIVELY LARGE, THE EXPRESSING OF LIQUID FROM THE MATERIAL TAKINGPLACE WHILE THE MATERIAL IS CARRIED BY THE ROTATION OF THE DISCS, ALONGTHE NARROWEST PORTION OF THE SPACE BETWEEN THE DISCS AND THEREAFTERDISCHARGED, THE DISCS BEING EACH PROVIDED WITH A PLURALITY OF SEPARATEPERIPHERALLY SPACED CELLS BEHIND THE PERFORATIONS, SAID CELLS BEINGFORMED BY INTERMEDIATE WALLS EXTENDING RADIALLY AND AXIALLY FROM THEDISCS ON THE SIDES THEREOF REMOTE FROM THE SPACE BETWEEN THE DISCS, SAIDCELLS BEING CLOSED BY WALLS EXTENDING SUBSTANTIALLY PARALLEL TO THEDISCS ON OPPOSITE SIDES OF SAID INTERMEDIATE WALLS, SAID CELLS IN EACHDISC BEING SEPARATED FROM ONE ANOTHER AND BEING OF SECTOR SHAPE, THECELLS HAVING ONE SIDE IN COMMUNICATION WITH THE PERFORATIONS AND THEOTHER SIDE PROVIDED WITH INDIVIDUAL PASSAGES SO LOCATED THAT DRAININGTHE LIQUID FROM ONE CELL TAKES PLACE DURING ONLY A PORTION OF ONEROTATION OF THE DISCS, A SUCTION SOURCE FOR AIDING IN SAID DRAINING,EACH OF SAID CELLS BEING PROVIDED WITH TWO OUTLET PASSAGES ARRANGED TODRAIN THE LIQUID FROM THE PERFORATIONS IN THE DISCS DURING DIFFERENTPORTIONS OF THE ROTATIONAL CYCLE WHEREBY THE LIQUID WILL FORM TWODIFFERENT FRACTIONS.